1. Field of the Invention
The present invention relates to a telemetry monitoring method and a device therefor for transmitting information by means of asynchronous transfer mode technique in a broadband integrated services digital network (B-ISDN).
Information from an apparatus for recording the readings of an instrument that is at a distance is transmitted in a cell form or in a fixed length packet form in a broadband integrated services digital network (abbreviated as B-ISDN). Accordingly, if the amount of information is increased, the number of cells is also increased. Note the case of a telemetric monitoring system, encoded data such as a picture and a speech are transmitted after a compression thereof.
2. Description of the Related Art
In general, a conventional telemetric monitoring apparatus includes a means for transmitting data of a picture, a sound or the like of a monitoring object by utilizing a communication circuit; a means for receiving the transmitted data by a monitoring device disposed at a distance; and a means for determining a normal or an abnormal state, through monitored pictures of the monitoring device, by a supervisor. Data of the picture or the sound of the monitoring object are collected by a television camera or a microphone. Alternatively various kinds of sensors may be arranged at separate parts of the monitoring object, and the outputs of these sensors delivered via a communication line.
A telemetry monitoring system through which a supervisor observes a monitoring picture, to thereby discriminate a normal state or an abnormal state, is manually operated and it is difficult to automate such a system. Accordingly, the costs of such a system are high, and often produces delays or a non-detection of an emergency. Often, alarm information is output from each sensor, i.e., an alarm is output when a sensor output becomes higher than a predetermined level when an emergency or accident occurs.
Nevertheless, such an output of alarm information is disadvantageous in that it takes a long time to determine the cause thereof after the alarm information has been received and displayed.
The Integrated Services Digital Network (abbreviated by ISDN) is one of the most important communication technique which supports an infrastructure (a social industrial subordinate parts) in a high-level information architecture society. One of the advanced ISDNs is a B-ISDN (broadband ISDN) which treats up to 150-600 Mbps signals. But the issue point that the present circuit switching system cannot overcome is switching system. Then, an asynchromous transfer mode (ATM) technique that is similar to a prior art packet exchange is developed and is the focus of the world's attention. Also, in the prior art synchronous transfer mode (STM) technique, a frame is constituted by a definite number of time slots and since one channel is used to utilize a particular time slot in a frame periodically, it is disadvantageous that information transmission speed is fixed to a definite value. The ATM technique is intended to eliminate such drawbacks.
In ATM communication, transfer information is divided into a fixed length of slot blocks to transfer and process. The fixed length of blocks for a unit of information is called a cell. The cell is divided into two kinds of parts; one is a region for storing transfer information per se and the other is a region in which information concerning a control for transferring cells is stored. The latter is regarded as a header which has a fixed length of a predetermined format and is added before an information field.
Multiplex communication per cell unit is carried out in an ATM device. Information within a header is employed in order to discriminate an address of cells which is multiplexed on a transmission line. Based on the existence of transfer information to some address, cells are delivered asynchronously. If information to be transferred is vacant, a vacant cell having no information in the information field is delivered. Therefore, a fixed length of cells are flowing continuously including the case of no information to be transferred. An observation of a header in a cell enables discriminating whether a cell is vacant or not and whether or not it is a cell including information of a logic channel in response any address.
As described above, a header includes address to multiplex or exchange thereby. In a conventional packet exchange system, a packet is of a variable length, and packet exchange is processed by a software, whereas since an ATM device is of a definite length, a cell appears periodically and the detection and exchange of cells are realized by a hardware to effect a high speed processing. A conventional circuit switching network has disadvantages that once a speed is determined it cannot be changed dynamically and must be a multiply of 64 K bit/sec, whereas if the number of cells delivered in ATM system is regulated to change a communication speed, the communication speed can be selected freely to set it dynamically.
The present invention has been devised as a way of eliminating such problems.